1. Field of the Invention
This invention relates to a compound semiconductor device and a method for manufacturing the same.
2. Background Art
Among compound semiconductors, nitride semiconductors have wide bandgap, and have greater electron saturation velocity than GaAs. Hence nitride semiconductors find widespread application in semiconductor light emitting apparatuses, high-frequency devices, and high-power switching devices.
In crystal growth for a nitride semiconductor device, GaN (gallium nitride), sapphire, and SiC (silicon carbide) substrates are used. These substrates have greater Young's modulus, and hence are harder, than GaAs and InP substrates. Furthermore, because of their hexagonal crystal structure, their cleavage directions are not orthogonal. For this reason, the process for separation into individual rectangular devices is more difficult than for other semiconductor materials.
JP-A 2005-136093(Kokai) discloses a method for separating rectangular devices where the needle tip of the scriber is made of diamond and scribe grooves are selectively formed on a bar-shaped semiconductor surface. In this method, an uncleaved surface occurs along the scribe groove, and a cleaved surface occurs in the region free from the scribe groove. Hence, by forming a scribe groove inside, an uncleaved surface is formed in the inner portion of the device side face, and a cleaved surface is formed in the outer portion of the device side face. Consequently, the device side face has a cleaved surface and an uncleaved surface. Thus an automatic assembling process is more difficult to implement, and processing residue occurring in the scribe process is not sufficiently reduced.
On the other hand, use of a YAG laser is also contemplated instead of scribing. However, increasing the laser power for separation with high yield may result in increasing debris, i.e., processing residue due to laser irradiation. It is necessary to reduce such debris for ensuring the reliability of semiconductor light emitting apparatuses.